Shrouded electrical fuses



2 Sheets-Sheet 1 Filed Feb. 1, 1961 --FIG. I.-

Y mveuroas John Feemm Eric Jacks.

BY 3 W & Ru-UL 6a SM,

Feb. 4, 1964 J. FEENAN ETAL 3,

SHROUDED ELECTRICAL FUSES Fiied Feb; 1, 1961 2 Shee ts-Sheet' 2 VE TOR John Feeuan s EncJacks.

:fication. have resulted in considerable reduction in the size of the wdmstaws Patent g.

i 3,120,593" 1 SI-IROUDED ELECTRICALFUSES John Feenan and Eric Jacks, Liverpool, England, assign- 01's to'The English ElectricCompany Limited, London, England, a British company Filed Feb. 1, 1961, Ser. No. 86,522 Claims priority, application Great Britain Feb. 20, 1960 2 Claims. (Cl. 200-132) fuses.

One known fuse of this type consists of a cylindrical ceramic body provided with inner end caps between which the fuse elements themselves extend along the inner bore of the ceramic body which is filled with silica sand. Copper tags are suitably connected to the ends of the fuse elements and the fuse is completed by the provision of outer end caps having slots on their plane surfaces through which the tags pass.

In the United States of America the specification [for the design of fuses of this type stipulates that for a given electrical rating of the fuse there shall be a minimum distance from the mid-point of the fuse to the nearest live part of the fuse. Since both the inner and outer end caps are made of electrically conducting material, the distance between the nearest parts of the outer end caps will be twice the minimum distance required by the speci- Recent developments in the design of fuses fuses so that for a given electrical rating, the distance from the mid-point of the fuse to the nearest live part is appreciably less than the required minimum value. This difficulty has been overcome by providing electrically-insulating shnouding arrangements for the fuse.

It is the object of the present invention to provide improved shrouding arrangements which not only enable the fuse to comply with the specification but which also facilitate maintaining the fuse at an even temperature.

According to the invention, in shrouding arrangements for high rupturing capacity electrical fuses of the type having a cylindrical ceramic body in which the fuse elements are mounted and copper tags secured to the ends of the fuse elements, the shrouding arrangements comprise two identical cup-like portions which are moulded in plastic material and which are arranged to interlock one with the other to enable them to be fitte'd over and completely cover the fuse, the copper tags projecting through slots provided in fiat surfaces of the cup-like portions.

According to a feature of the invention the two cuplike portions are shaped internally so that passages are provided for the circulation of air between the (fuse and the internal surface of the cup-like portions. This enables the fuse .to be maintained at an even temperature and provides a quicker acting fuse.

The invention will be better understood from the following description of one embodiment taken in conjunctionwith the accompanying drawings comprising FIGS. 1 to 4. In the drawings,

FIG. 1 shows a part sectional and part external view of the fuse with the shrouding arrangements in position. The upper left hand portion of FIG. 1 shows a section through one of the cup-like portions of the shrouding arrangement; the upper right hand portion of FIG. 1 shows a section through the outer end cap of the fuse; the lower left hand portion of FIG. 1 shows a section through one cup-like portion and the fuse, while the lower right hand portion of FIG. 1 shows an external view of one cup-like portion.

FIG. 2 shows a plan view of the interior of one cuplikeporti'on looking in the direction of the arrows A, A ofFlGal, l I

F1643. shows FIG-.34 shows a plan view of the top surface of the cup-like portionap Referring ;first to i the :fuse itself consists 1 of a 1 cylindricalaceramic body. :1 011 provided at eachend with- 1 inner caps 11 1 recessed at 12, the recess having an aperture. 1-3 for the reception of the fuse elements 14. The fuse; elements 14 are bent over the edge of the aperture andi the recess '12 is closed by a member 15 formed integral: with the connecting tag 16. Electrical connection be-- tween the fuse elements and the tag is effected by deposit-- ing solder in the base of the recess 12 in the inner cap 11'. and applying heat subsequent to the fitting of the tag; whereupon the solder melts and ensures a good electrical connection between the fuse elements and the tag. The: fuse itself is completed by an outer cap 17 provided with a slot in its plane surface through which the tag passes. The shrouding arrangements for the fuse consist of two identical cups 18 which are moulded from a suitable plastic material, such as nylon. The open edges of the cups are recessed to form an engaging lip and over slightly less than the lip is continuous. with the outer surface of the shroud, as shown at :19 (FIGS. 1 and 3), while for slightly less than the remaining 180 the lip is continuous with the inner surface of the shroud, as shown at 20 (:FIGS. 1 and 3). A slight clearance is provided as. indicated at 21 (FIGS. 1 and 3), at the point on the edge.- of the cup Where the lips change.

Internally the cups are provided with four ribs 22. (FIGS. 1, 2 and 3) and the ribs are stepped as shown at 23 FIGS. 1 and 3), to provide a seating for the outer cap 17 of the fuse. The top surface of the cup is pro-- vided with an aperture 24 defined by an inturned lip 25 of the cup. The longer dimension of the aperture 24 is substantially equal to the width of a tag 16 so that in assembling the shroud around the fuse, the tag passes through the aperture 24.

It will be understood that when assembling the shroud the two cups will be arranged with their corresponding lips r180 apart so that the two cups lock together in the manner shown in FIG. 1. When the two cups are completely engaged the two outer caps of the fuse will abut against the stepped portions '23 on the ribs 22 of the shroud and the flexibility of the plastic, material is sufficient to exert a slight gripping action on the ends of the fuse so that it is firmly held within the cups. The two cups are bonded together over their interlocking edges by means of a suitable adhesive. It will, of course, be understood that the distance between the plane surfaces of the two cups when completely engaged must be at least; twice the minimum distance given in the previously-men tioned specification as determined by the rating of the fuse. A further advantage of the invention is that the shrouding arrangements enable the fuse to be handled with complete safety, for instance, by gripping it about the centre of the shroud.

It will be seen from FIG. 1 that with the construction of the shrouding arrangements. according to the present invention there is a passage between the inner walls of the cups and the outer surface of the fuse and this enables.

a circulation of air to take place. It is found that the provision of an air circulation passage of this nature assists considerably in lowering the temperature of the fuse when connected in an external circuit.

We claim:

1. In combination in a high rupturing capacity electric 3,1 0 93 Patented. Feb. 4,1964 f a sectional view..of one cup-like'portion looking in the. directionofvth'earrows B, B'iof FIG. 2, and

in a recess in each said closure cap and in engagement with said fuse element and a shrouding arrangement comprising two identical cup-like portions formed of plastic material, means interlocking one cup-like portion with the other to: fit over and completely cover the fuse, flat surfaces on said cup-like portions having slots through which the copper tags project and internal ribs on each cup-like portion, said internal ribs being provided with shoulders against which one end of the fuse abuts.

2. The combination as claimed in claim -1 wherein the 10 References Cited in the file of this patent UNITED STATES PATENTS Woodruff Mar. 31,

Kozacka et a1 June 15,

Matthysse July 6,

Erdtmann et a1. Nov. 24,

FOREIGN PATENTS Australia Feb. 17, 

1. IN COMBINATION IN A HIGH RUPTURING CAPACITY ELECTRIC FUSE, AT LEAST ONE FUSE ELEMENT, A CYLINDICAL CERAMIC BODY IN WHICH SAID FUSE ELEMENT IS MOUNTED, A CLOSURE CAP FOR EACH END OF SAID CERAMIC BODY, A COPPER TAG SECURED WITHIN A RECESS IN EACH SAID CLOSURE CAP AND IN ENGAGEMENT WITH SAID FUSE ELEMENT AND A SHROUDING ARRANGEMENT COMPRISING TWO IDENTICAL CUP-LIKE PORTIONS FORMED OF PLASTIC MATERIAL, MEANS INTERLOCKING ONE CUP-LIKE PORTION WITH THE OTHER TO FIT OVER AND COMPLETELY COVER THE FUSE, FLAT SURFACES ON SAID CUP-LIKE PORTIONS HAVING SLOTS THROUGH WHICH THE COPPER TAGS PROJECT AND INTERNAL RIBS ON EACH CUP-LIKE PORTION, SAID INTERNAL RIBS BEING PROVIDED WITH SHOULDERS AGAINST WHICH ONE END OF THE FUSE ABUTS. 